Which among the following represent the changes in pulmonary respiratory parameters with aging?
Correct Answer: A
The following diagram depicts various lung volumes and capacities:
Functional residual capacity (FRC) is the volume of the lungs at the end of passive expiration. It is a sum of residual volume and expiratory reserve volume. FRC is determined by a balance between the inward “elastic recoil” force of the lung parenchymal tissue and the outward “passive recoil” force from the ribs, joints, and chest wall muscle. The FRC slightly increases with age and height. FRC is decreased with supine position, obesity, and the female sex.
Closing capacity is the point in which small airways start to close during expiration. With age, airway closing happens at a larger lung volume therefore closing capacity increases (approaches FRC). Closing of the small airways can happen at or above FRC around the age of 65 to 70 years, and this is partially what contributes to decreased oxygenation with aging. Closing capacity is independent of position.
Reference:
A 62-year-old male with past medical history significant for diabetes, hypertension, hyperlipidemia, and 60 pack year smoking history comes in with complaints of respiratory distress and flu-like symptoms for the past week. Vitals are:
He is intermittently confused but is arousable and redirectable. His arterial blood gas shows:
Which is the appropriate next step in intervention?
Correct Answer: D
The patient is experiencing COPD exacerbation likely brought on by recent flu. The patient’s ABG is showing respiratory acidosis, and it would be most beneficial to start noninvasive bilevel positive pressure ventilation in this case.
NIPPV refers to a mode of ventilation in which positive pressure is delivered to the patient through a noninvasive mask interface (face mask, nasal pillow) compared to an invasive mode of ventilation (endotracheal tube, laryngeal mask, tracheostomy). Randomized controlled trials and meta-analysis have shown that NIPPV improves important clinical outcomes (mortality, rate of intubation, hospital length of stay) in patients having an acute exacerbation of COPD complicated by hypercapnic acidosis. Specific indications for NIPPV include COPD exacerbation with respiratory acidosis, cardiogenic pulmonary edema, and acute hypoxemic respiratory failure. Contraindications to NIPPV include cardiac or respiratory arrest, altered mental status, inability to clear airway secretions or protect airway, facial trauma, recent esophageal surgery, and high aspiration risk.
Although high flow nasal cannula has shown to provide patients with some degree of PEEP and improve oxygenation, the patient’s primary problem in this case is hypercapnic respiratory failure, and HFNC is less efficacious in improving hypercapnia compared to NIPPV. Heliox can improve the patient’s respiratory distress by delivering less-dense oxygen hence reducing resistance to airway flow. Although this may reduce the work of breathing for the patient, it would not improve the patient’s hypercapnis brought on by COPD exacerbation. Intubation of the patient is not indicated at this point because the patient is hemodynamically stable and mentation is grossly intact.
Although steroids and antibiotics may be indicated in certain situations (severe COPD exacerbation with active sputum production, increased dyspnea), attempts to improve the patient’s respiratory acidosis should be the primary focus at this point.
References:
A 81-year-old female with history of atrial fibrillation on Coumadin, hypertension, and recent hip fracture from a fall s/p trochanteric fixation of the femoral head who has been recovering in a skilled nursing facility is brought into the emergency department (ED) with complaints of altered mental status, high fevers, and productive cough. The patient is emergently intubated because of lethargy and is transferred to the ICU. On arrival to the ICU, the patient’s vitals are HR 110 bpm, BP 90/65 mm Hg, SpO2 91% on 60% FiO2 on the ventilator. ABG is showing pH of 7.38, PaO2 of 88 mm Hg, PaCO2 of 39 mm Hg, and HCO3 of 22. Despite an increase of the FiO2 on the ventilator, increase of PEEP, and repositioning of the ETT, the patient’s oxygenation does not improve. A decision to obtain a CXR is made and the imaging obtained below:
What is the next appropriate intervention given these clinical findings?
Based on the chest X-ray obtained, the patient’s hypoxemia is due to left lower lobe collapse. Given the patient’s history of productive cough and purulent sputum, left lower lobe collapse is likely from mucous plugging, and bronchoscopy to clear the mucous plug is advised.
Left lower lobe collapse can be difficult to identify at times because of the cardiac shadow. The features to observe when left lower lobe is suspected is a triangular opacity in the posterior medial aspect of the left lung, a “double cardiac contour,” loss of normal hemidiaphragmatic silhouette, or loss of the outline of the descending aorta. These features are also similar to how atelectasis would look on chest X-ray, so clinical correlation is necessary to distinguish between differential diagnosis of hypoxemia. In cases of lobe collapse due to mucous plugging, therapeutic bronchoscopy would be necessary to suction out the mucous plug. Although suctioning the endotracheal tube can partially alleviate symptoms of hypoxemia and mucous plugging, the suction catheter is limited in terms of the depth and specific location it can reach.
In case of a tension pneumothorax, contralateral shift of the mediastinum, increase in ipsilateral pleural space, and depression of the hemidiaphragm may be observed. If the tension pneumothorax is significant enough then it can also cause hemodynamic compromise. If a tension pneumothorax is suspected then a chest tube should be immediately inserted to the affected side to relieve the pneumothorax. If a chest tube is not readily available or if one is not familiar with insertion of a chest tube, then needle decompression should be immediately performed while help is called for. Needle decompression is typically performed with a large bore catheter needle, and it is inserted into the second intercostal space of the affected side along the mid-clavicular line.
Changing the patient’s position from supine to prone is a technique that can be adopted to improve patient’s oxygenation and V/Q mismatch. It is often employed as an adjunctive measure in patients with severe ARDS. Movement of the endotracheal is not uncommon in the ICU setting. Especially with prolonged intubation, the endotracheal tube becomes warm and can be easily kinked or deformed. Movement of the ETT further into the trachea can cause right main stem intubation and can lead to hypoxemia and atelectasis of the contralateral lung, whereas movement of the ETT away from the carina can lead to air leaks and delivery of inadequate tidal volumes. Placement of ETT can be verified by listening to bilateral breath sounds, chest X-ray, or bronchoscopy
A 92-year-old female with mild dementia, atrial fibrillation on warfarin, and hypertension presents to the ED after suffering a mechanical fall after tripping over a rug at her nursing home. Chest X-ray reveals mildly displaced right-sided rib fractures from ribs 4 through 10. Her vital signs are:
Arterial blood gas obtained shows:
The patient is mildly confused and is only oriented toward self and place. The patient is complaining of shortness of breath and rib pain with every breath and continues to take rapid shallow breaths. She is also complaining of discomfort with the face mask and attempts to remove the face mask despite redirection.
Given this clinical scenario, what would be the next appropriate clinical
Correct Answer: E
Given the patient’s hypoxemia and mild confusion with complaints of discomfort of a face mask, applying a heated and humidified HFNC cannula would be the most appropriate treatment for this patient. There are two main mechanisms to deliver oxygen: low-flow system versus high-flow system. Low-flow systems include nasal cannula and conventional oxygen face mask. High-flow system includes non-rebreather face mask, Venturi mask, and heated/humidified HFNC.
HFNC delivers heated and humidified oxygen at extremely high flow rates to minimize entrainment of room air. Patients who are in respiratory distress often times generate high inspiratory flow rates that exceed the oxygen flow rates of conventional oxygen delivery systems leading to entrainment of room air and reduction in the FiO2 of oxygen delivered to the patient, contributing to hypoxemia. HFNC overcomes this issue by generating oxygen flow rates that are higher than the patient’s inspiratory flow rate resulting in reliable and titratable FiO2 delivery. HFNC is heated and humidified, which can promote clearance of secretions/mucous, decrease damage to the epithelial cells of the airway, and decrease work of breathing compared to the Venturi mask or a non-rebreather mask. The heat and the humidity along with the nasal prongs improves comfort for the patient. HFNC also has the added benefit of CPAP (for every 10 L/min flow increase, 0.7 cm H2O of PEEP is added) and wash out of nasopharyngeal deadspace. Given the patient’s mild confusion with complaints of discomfort with the face mask, HFNC would be the best option for the patient to improve her oxygenation.
Venturi mask and non-rebreather masks are also considered high oxygen flow systems, but compared to HFNC, heating and humidification of oxygen is less effective hence leading to more discomfort for the patient. The wash out effect of the nasopharynx is also less leading to less fractional area available for effective gas exchange. Also both systems utilize a face mask that can add discomfort to patients who feel claustrophobic with a tight fitting mask.
BiPAP has similar benefits of HFNC and can deliver high amounts of positive pressure for respiratory support. BiPAP can also be utilized to improve hypercapnia, whereas HFNC is less effective in improving ventilation. Although BiPAP is not an unreasonable option for this patient, given the patient’s complaint of discomfort with the face mask and no significant issues with the patient’s ventilation status at this time, a trial of HFNC would be more reasonable at this time over BIPAP. If the patient’s respiratory status continues to decline, then escalation to BIPAP would be reasonable.
A 62-year-old male with past medical history significant for end stage liver disease secondary to alcohol abuse, portopulmonary syndrome, GI bleed, COPD, and type 2 diabetes presents to the ED with hematemesis. The patient is intubated for airway protection and is transferred up to the ICU for close monitoring. Gastroenterology specialists plan to perform an upper GI endoscopy to determine the etiology of the upper GI bleed. The patient is sedated on 30 mg/kg/min of propofol. The patient’s vital signs are:
Ventilator settings are pressure control, tidal volume 700 mL, RR 14, FiO2 100%, PEEP 3 mm H2O. You walk into the patient’s room and notice these waveforms on the ventilator (see figure that follows). There are no ventilator or monitor alarms going off in the patient’s room.
Given these findings, what is the next appropriate step in ventilator management?
Based on the diagram presented above, the patient is ineffectively trigging the ventilator because of auto-PEEP. Given the answer choices, lowering tidal volumes would be the next appropriate step to improve the patient’s ventilator dysynchrony. Accurate assessment of patient-ventilator interactions and work of breathing is important in improving the patient comfort on the ventilator and to optimizing ventilator settings to achieve swift liberation from mechanical ventilator. The modern ventilator has many different modes of ventilation and many parameters that the physician can input to optimize ventilator support. Modern ventilators are also capable of displaying many real-time information including pressure-time graphs, flow-time graphs, and volume-time graphs. Using these types of various information, a physician’s goal is to achieve patient-ventilator synchrony where the ventilator-assisted breathing coincides well with the patient’s intrinsic breathing efforts. When the patient’s inspiratory effort does not match with the ventilator triggered support, it is said that ventilator asynchrony has occurred. There are three main types of ventilator asynchrony: triggerasynchrony, flow-asynchrony, and cycling-asynchrony.
Trigger asynchrony include ineffective triggering, double triggering, or auto-triggering. Ineffective triggering occurs when the patient attempts to initiate a breath, but the trigger threshold is not reached and the ventilator fails to trigger an effective breath. Ineffectively triggered breaths are not accounted for by the ventilator as respiratory rate and typically do not cause the ventilator to alarm. In the graph displayed in the question, two different respiratory wave forms can be observed. The effectively triggered breaths generate the set tidal volume of 700 mL. On the other hand, ineffectively triggered breaths produce a deflection in the pressure-time and flow-time graphs, but the set tidal volume is not achieved, leading to a trigger asynchrony. Also by observing the volume-time graph, one can conclude that the patient’s inspiratory efforts (shown by deflection in the flow and pressure loops) are triggered before complete exhalation (volume loop does not return to baseline level of 0 before the deflection of pressure and flow loops) resulting in auto-PEEP. Air trapping due to insufficient exhalation time leading to auto-PEEP is a common cause of ventilator asynchrony in patients with a history of COPD. The ways to prevent auto-PEEP, therefore improve patient-ventilator synchrony, is to prolong expiratory time by adjusting the I:E ratio or by reducing tidal volume to allow complete exhalation.
Double-triggering occurs when a patient’s inspiratory effort continues throughout the preset ventilator inspiratory time and remains present after ventilator inspiratory time has finished. Auto-triggering occurs when the ventilator delivers an assisted breath that was not initiated by the patient. Flow asynchrony may be due to ventilator flow being either too fast or too slow for the patient and may occur with either flow-targeted breaths or with pressure-targeted breaths.
Cycling refers to termination of ventilator-assisted inspiration. A patient’s inspiratory effort may still be present at the time of termination of assisted inspiration. This termination of assisted breathing despite the patient’s continued effort is referred to as premature cycling (the reference point is the patient and not the ventilator).
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